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      1 /*
      2  * Copyright  2010,2012  Google, Inc.
      3  *
      4  *  This is part of HarfBuzz, a text shaping library.
      5  *
      6  * Permission is hereby granted, without written agreement and without
      7  * license or royalty fees, to use, copy, modify, and distribute this
      8  * software and its documentation for any purpose, provided that the
      9  * above copyright notice and the following two paragraphs appear in
     10  * all copies of this software.
     11  *
     12  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
     13  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
     14  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
     15  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
     16  * DAMAGE.
     17  *
     18  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
     19  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
     20  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
     21  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
     22  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
     23  *
     24  * Google Author(s): Behdad Esfahbod
     25  */
     26 
     27 #include "hb-ot-shape-complex-private.hh"
     28 
     29 
     30 /* Thai / Lao shaper */
     31 
     32 
     33 /* PUA shaping */
     34 
     35 
     36 enum thai_consonant_type_t
     37 {
     38   NC,
     39   AC,
     40   RC,
     41   DC,
     42   NOT_CONSONANT,
     43   NUM_CONSONANT_TYPES = NOT_CONSONANT
     44 };
     45 
     46 static thai_consonant_type_t
     47 get_consonant_type (hb_codepoint_t u)
     48 {
     49   if (u == 0x0E1Bu || u == 0x0E1Du || u == 0x0E1Fu/* || u == 0x0E2Cu*/)
     50     return AC;
     51   if (u == 0x0E0Du || u == 0x0E10u)
     52     return RC;
     53   if (u == 0x0E0Eu || u == 0x0E0Fu)
     54     return DC;
     55   if (hb_in_range (u, 0x0E01u, 0x0E2Eu))
     56     return NC;
     57   return NOT_CONSONANT;
     58 }
     59 
     60 
     61 enum thai_mark_type_t
     62 {
     63   AV,
     64   BV,
     65   T,
     66   NOT_MARK,
     67   NUM_MARK_TYPES = NOT_MARK
     68 };
     69 
     70 static thai_mark_type_t
     71 get_mark_type (hb_codepoint_t u)
     72 {
     73   if (u == 0x0E31u || hb_in_range (u, 0x0E34u, 0x0E37u) ||
     74       u == 0x0E47u || hb_in_range (u, 0x0E4Du, 0x0E4Eu))
     75     return AV;
     76   if (hb_in_range (u, 0x0E38u, 0x0E3Au))
     77     return BV;
     78   if (hb_in_range (u, 0x0E48u, 0x0E4Cu))
     79     return T;
     80   return NOT_MARK;
     81 }
     82 
     83 
     84 enum thai_action_t
     85 {
     86   NOP,
     87   SD,  /* Shift combining-mark down */
     88   SL,  /* Shift combining-mark left */
     89   SDL, /* Shift combining-mark down-left */
     90   RD   /* Remove descender from base */
     91 };
     92 
     93 static hb_codepoint_t
     94 thai_pua_shape (hb_codepoint_t u, thai_action_t action, hb_font_t *font)
     95 {
     96   struct thai_pua_mapping_t {
     97     hb_codepoint_t u;
     98     hb_codepoint_t win_pua;
     99     hb_codepoint_t mac_pua;
    100   } const *pua_mappings = NULL;
    101   static const thai_pua_mapping_t SD_mappings[] = {
    102     {0x0E48u, 0xF70Au, 0xF88Bu}, /* MAI EK */
    103     {0x0E49u, 0xF70Bu, 0xF88Eu}, /* MAI THO */
    104     {0x0E4Au, 0xF70Cu, 0xF891u}, /* MAI TRI */
    105     {0x0E4Bu, 0xF70Du, 0xF894u}, /* MAI CHATTAWA */
    106     {0x0E4Cu, 0xF70Eu, 0xF897u}, /* THANTHAKHAT */
    107     {0x0E38u, 0xF718u, 0xF89Bu}, /* SARA U */
    108     {0x0E39u, 0xF719u, 0xF89Cu}, /* SARA UU */
    109     {0x0E3Au, 0xF71Au, 0xF89Du}, /* PHINTHU */
    110     {0x0000u, 0x0000u, 0x0000u}
    111   };
    112   static const thai_pua_mapping_t SDL_mappings[] = {
    113     {0x0E48u, 0xF705u, 0xF88Cu}, /* MAI EK */
    114     {0x0E49u, 0xF706u, 0xF88Fu}, /* MAI THO */
    115     {0x0E4Au, 0xF707u, 0xF892u}, /* MAI TRI */
    116     {0x0E4Bu, 0xF708u, 0xF895u}, /* MAI CHATTAWA */
    117     {0x0E4Cu, 0xF709u, 0xF898u}, /* THANTHAKHAT */
    118     {0x0000u, 0x0000u, 0x0000u}
    119   };
    120   static const thai_pua_mapping_t SL_mappings[] = {
    121     {0x0E48u, 0xF713u, 0xF88Au}, /* MAI EK */
    122     {0x0E49u, 0xF714u, 0xF88Du}, /* MAI THO */
    123     {0x0E4Au, 0xF715u, 0xF890u}, /* MAI TRI */
    124     {0x0E4Bu, 0xF716u, 0xF893u}, /* MAI CHATTAWA */
    125     {0x0E4Cu, 0xF717u, 0xF896u}, /* THANTHAKHAT */
    126     {0x0E31u, 0xF710u, 0xF884u}, /* MAI HAN-AKAT */
    127     {0x0E34u, 0xF701u, 0xF885u}, /* SARA I */
    128     {0x0E35u, 0xF702u, 0xF886u}, /* SARA II */
    129     {0x0E36u, 0xF703u, 0xF887u}, /* SARA UE */
    130     {0x0E37u, 0xF704u, 0xF888u}, /* SARA UEE */
    131     {0x0E47u, 0xF712u, 0xF889u}, /* MAITAIKHU */
    132     {0x0E4Du, 0xF711u, 0xF899u}, /* NIKHAHIT */
    133     {0x0000u, 0x0000u, 0x0000u}
    134   };
    135   static const thai_pua_mapping_t RD_mappings[] = {
    136     {0x0E0Du, 0xF70Fu, 0xF89Au}, /* YO YING */
    137     {0x0E10u, 0xF700u, 0xF89Eu}, /* THO THAN */
    138     {0x0000u, 0x0000u, 0x0000u}
    139   };
    140 
    141   switch (action) {
    142     default: assert (false); /* Fallthrough */
    143     case NOP: return u;
    144     case SD:  pua_mappings = SD_mappings; break;
    145     case SDL: pua_mappings = SDL_mappings; break;
    146     case SL:  pua_mappings = SL_mappings; break;
    147     case RD:  pua_mappings = RD_mappings; break;
    148   }
    149   for (; pua_mappings->u; pua_mappings++)
    150     if (pua_mappings->u == u)
    151     {
    152       hb_codepoint_t glyph;
    153       if (hb_font_get_glyph (font, pua_mappings->win_pua, 0, &glyph))
    154 	return pua_mappings->win_pua;
    155       if (hb_font_get_glyph (font, pua_mappings->mac_pua, 0, &glyph))
    156 	return pua_mappings->mac_pua;
    157       break;
    158     }
    159   return u;
    160 }
    161 
    162 
    163 static enum thai_above_state_t
    164 {     /* Cluster above looks like: */
    165   T0, /*                        */
    166   T1, /*                        */
    167   T2, /*                        */
    168   T3, /*                        */
    169   NUM_ABOVE_STATES
    170 } thai_above_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] =
    171 {
    172   T0, /* NC */
    173   T1, /* AC */
    174   T0, /* RC */
    175   T0, /* DC */
    176   T3, /* NOT_CONSONANT */
    177 };
    178 
    179 static const struct thai_above_state_machine_edge_t {
    180   thai_action_t action;
    181   thai_above_state_t next_state;
    182 } thai_above_state_machine[NUM_ABOVE_STATES][NUM_MARK_TYPES] =
    183 {        /*AV*/    /*BV*/    /*T*/
    184 /*T0*/ {{NOP,T3}, {NOP,T0}, {SD, T3}},
    185 /*T1*/ {{SL, T2}, {NOP,T1}, {SDL,T2}},
    186 /*T2*/ {{NOP,T3}, {NOP,T2}, {SL, T3}},
    187 /*T3*/ {{NOP,T3}, {NOP,T3}, {NOP,T3}},
    188 };
    189 
    190 
    191 static enum thai_below_state_t
    192 {
    193   B0, /* No descender */
    194   B1, /* Removable descender */
    195   B2, /* Strict descender */
    196   NUM_BELOW_STATES
    197 } thai_below_start_state[NUM_CONSONANT_TYPES + 1/* For NOT_CONSONANT */] =
    198 {
    199   B0, /* NC */
    200   B0, /* AC */
    201   B1, /* RC */
    202   B2, /* DC */
    203   B2, /* NOT_CONSONANT */
    204 };
    205 
    206 static const struct thai_below_state_machine_edge_t {
    207   thai_action_t action;
    208   thai_below_state_t next_state;
    209 } thai_below_state_machine[NUM_BELOW_STATES][NUM_MARK_TYPES] =
    210 {        /*AV*/    /*BV*/    /*T*/
    211 /*B0*/ {{NOP,B0}, {NOP,B2}, {NOP, B0}},
    212 /*B1*/ {{NOP,B1}, {RD, B2}, {NOP, B1}},
    213 /*B2*/ {{NOP,B2}, {SD, B2}, {NOP, B2}},
    214 };
    215 
    216 
    217 static void
    218 do_thai_pua_shaping (const hb_ot_shape_plan_t *plan HB_UNUSED,
    219 		     hb_buffer_t              *buffer,
    220 		     hb_font_t                *font)
    221 {
    222   thai_above_state_t above_state = thai_above_start_state[NOT_CONSONANT];
    223   thai_below_state_t below_state = thai_below_start_state[NOT_CONSONANT];
    224   unsigned int base = 0;
    225 
    226   hb_glyph_info_t *info = buffer->info;
    227   unsigned int count = buffer->len;
    228   for (unsigned int i = 0; i < count; i++)
    229   {
    230     thai_mark_type_t mt = get_mark_type (info[i].codepoint);
    231 
    232     if (mt == NOT_MARK) {
    233       thai_consonant_type_t ct = get_consonant_type (info[i].codepoint);
    234       above_state = thai_above_start_state[ct];
    235       below_state = thai_below_start_state[ct];
    236       base = i;
    237       continue;
    238     }
    239 
    240     const thai_above_state_machine_edge_t &above_edge = thai_above_state_machine[above_state][mt];
    241     const thai_below_state_machine_edge_t &below_edge = thai_below_state_machine[below_state][mt];
    242     above_state = above_edge.next_state;
    243     below_state = below_edge.next_state;
    244 
    245     /* At least one of the above/below actions is NOP. */
    246     thai_action_t action = above_edge.action != NOP ? above_edge.action : below_edge.action;
    247 
    248     if (action == RD)
    249       info[base].codepoint = thai_pua_shape (info[base].codepoint, action, font);
    250     else
    251       info[i].codepoint = thai_pua_shape (info[i].codepoint, action, font);
    252   }
    253 }
    254 
    255 
    256 static void
    257 preprocess_text_thai (const hb_ot_shape_plan_t *plan,
    258 		      hb_buffer_t              *buffer,
    259 		      hb_font_t                *font)
    260 {
    261   /* This function implements the shaping logic documented here:
    262    *
    263    *   http://linux.thai.net/~thep/th-otf/shaping.html
    264    *
    265    * The first shaping rule listed there is needed even if the font has Thai
    266    * OpenType tables.  The rest do fallback positioning based on PUA codepoints.
    267    * We implement that only if there exist no Thai GSUB in the font.
    268    */
    269 
    270   /* The following is NOT specified in the MS OT Thai spec, however, it seems
    271    * to be what Uniscribe and other engines implement.  According to Eric Muller:
    272    *
    273    * When you have a SARA AM, decompose it in NIKHAHIT + SARA AA, *and* move the
    274    * NIKHAHIT backwards over any tone mark (0E48-0E4B).
    275    *
    276    * <0E14, 0E4B, 0E33> -> <0E14, 0E4D, 0E4B, 0E32>
    277    *
    278    * This reordering is legit only when the NIKHAHIT comes from a SARA AM, not
    279    * when it's there to start with. The string <0E14, 0E4B, 0E4D> is probably
    280    * not what a user wanted, but the rendering is nevertheless nikhahit above
    281    * chattawa.
    282    *
    283    * Same for Lao.
    284    *
    285    * Note:
    286    *
    287    * Uniscribe also does some below-marks reordering.  Namely, it positions U+0E3A
    288    * after U+0E38 and U+0E39.  We do that by modifying the ccc for U+0E3A.
    289    * See unicode->modified_combining_class ().  Lao does NOT have a U+0E3A
    290    * equivalent.
    291    */
    292 
    293 
    294   /*
    295    * Here are the characters of significance:
    296    *
    297    *			Thai	Lao
    298    * SARA AM:		U+0E33	U+0EB3
    299    * SARA AA:		U+0E32	U+0EB2
    300    * Nikhahit:		U+0E4D	U+0ECD
    301    *
    302    * Testing shows that Uniscribe reorder the following marks:
    303    * Thai:	<0E31,0E34..0E37,0E47..0E4E>
    304    * Lao:	<0EB1,0EB4..0EB7,0EC7..0ECE>
    305    *
    306    * Note how the Lao versions are the same as Thai + 0x80.
    307    */
    308 
    309   /* We only get one script at a time, so a script-agnostic implementation
    310    * is adequate here. */
    311 #define IS_SARA_AM(x) (((x) & ~0x0080u) == 0x0E33u)
    312 #define NIKHAHIT_FROM_SARA_AM(x) ((x) - 0x0E33u + 0x0E4Du)
    313 #define SARA_AA_FROM_SARA_AM(x) ((x) - 1)
    314 #define IS_TONE_MARK(x) (hb_in_ranges ((x) & ~0x0080u, 0x0E34u, 0x0E37u, 0x0E47u, 0x0E4Eu, 0x0E31u, 0x0E31u))
    315 
    316   buffer->clear_output ();
    317   unsigned int count = buffer->len;
    318   for (buffer->idx = 0; buffer->idx < count;)
    319   {
    320     hb_codepoint_t u = buffer->cur().codepoint;
    321     if (likely (!IS_SARA_AM (u))) {
    322       buffer->next_glyph ();
    323       continue;
    324     }
    325 
    326     /* Is SARA AM. Decompose and reorder. */
    327     hb_codepoint_t decomposed[2] = {hb_codepoint_t (NIKHAHIT_FROM_SARA_AM (u)),
    328 				    hb_codepoint_t (SARA_AA_FROM_SARA_AM (u))};
    329     buffer->replace_glyphs (1, 2, decomposed);
    330     if (unlikely (buffer->in_error))
    331       return;
    332 
    333     /* Make Nikhahit be recognized as a mark when zeroing widths. */
    334     unsigned int end = buffer->out_len;
    335     _hb_glyph_info_set_general_category (&buffer->out_info[end - 2], HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK);
    336 
    337     /* Ok, let's see... */
    338     unsigned int start = end - 2;
    339     while (start > 0 && IS_TONE_MARK (buffer->out_info[start - 1].codepoint))
    340       start--;
    341 
    342     if (start + 2 < end)
    343     {
    344       /* Move Nikhahit (end-2) to the beginning */
    345       buffer->merge_out_clusters (start, end);
    346       hb_glyph_info_t t = buffer->out_info[end - 2];
    347       memmove (buffer->out_info + start + 1,
    348 	       buffer->out_info + start,
    349 	       sizeof (buffer->out_info[0]) * (end - start - 2));
    350       buffer->out_info[start] = t;
    351     }
    352     else
    353     {
    354       /* Since we decomposed, and NIKHAHIT is combining, merge clusters with the
    355        * previous cluster. */
    356       if (start)
    357 	buffer->merge_out_clusters (start - 1, end);
    358     }
    359   }
    360   buffer->swap_buffers ();
    361 
    362   /* If font has Thai GSUB, we are done. */
    363   if (plan->props.script == HB_SCRIPT_THAI && !plan->map.found_script[0])
    364     do_thai_pua_shaping (plan, buffer, font);
    365 }
    366 
    367 const hb_ot_complex_shaper_t _hb_ot_complex_shaper_thai =
    368 {
    369   "thai",
    370   NULL, /* collect_features */
    371   NULL, /* override_features */
    372   NULL, /* data_create */
    373   NULL, /* data_destroy */
    374   preprocess_text_thai,
    375   HB_OT_SHAPE_NORMALIZATION_MODE_DEFAULT,
    376   NULL, /* decompose */
    377   NULL, /* compose */
    378   NULL, /* setup_masks */
    379   HB_OT_SHAPE_ZERO_WIDTH_MARKS_DEFAULT,
    380   false,/* fallback_position */
    381 };
    382